A capacitor for an implantable medical device is presented. The capacitor includes an anode, a cathode, a separator therebetween, and an electrolyte over the anode, cathode, and separator. The electrolyte includes ingredients comprising acetic acid, ammonium acetate, phosphoric acid, and tetraethylene glycol dimethyl ether. The capacitor has an operating voltage ninety percent or greater of its formation voltage.